hi all,
a few weeks ago i had a hot water cylinder moved a short distance from where it was (bathroom airing cupboard) to another cupboard on the same landing about six feet,now can anyone help please as when i put the boiler in hot water only the upstairs rads are getting hot as well,could the flow and return pipes be crossed?
many thanks.

I take it, it's a gravity hot water system. With gravity hot water systems you can get abit heat in the upstairs radiators, this is just because heat rises and travels up the central heating flow pipe from the boiler.

With moving the cylinder there will probably more resistance to the water travelling up the primary flow to the cylinder, so some heat is being lost to the central heating flow, heating the radiators.

The easiest way to solve this is to bend a pipe to form like a trap on the central heating flow pipe right next to the boiler. As the pipe drops before it rises it will prevent any natural (gravity) circulation.

thanks htg engineer,the sytem is fully pumped,ideal mexico floor standing boiler which pre move of the hot cylinder worked fine,but the rads upstairs are not just warm they are red hot as if the heating is on but only upstairs,the only other thing is we connected a towel rad to the flow and return pipes jus before they enter the cylinder,could this be the problem? many thanks for your reply
kev_1911